The invention relates to an automotive electrical alternator, and particularly to an alternator having coolant channels adapted to pass engine coolant therethrough to cool the alternator.
This invention is related to an electrical alternator, particularly adapted for use in motor vehicle applications including passenger cars and light trucks. These devices are typically mechanically driven using a drive belt wrapped on a pulley connected to the crankshaft of the vehicle""s internal combustion engine. The belt drives a pulley on the alternator which rotates an internal rotor assembly to generate alternating current (AC) electrical power. This alternating current electrical power is rectified to direct current (DC) and supplied to the motor vehicle""s electrical bus and storage battery.
While alternators have been in use in motor vehicles for many decades, today""s demands on motor vehicle design, cost, and performance have placed increasing emphasis on the design of more efficient alternators. Today""s motor vehicles feature a dramatic increase in the number of electrical on-board systems and accessories. Such electrical devices include interior and exterior lighting, climate control systems; increasingly sophisticated powertrain control systems, vehicle stability systems, traction control systems, and anti-lock brake systems. Vehicle audio and telematics systems place further demands on the vehicle""s electrical system. Still further challenges in terms of the output capacity of the motor vehicle""s electrical alternators will come with the widespread adoption of electrically assisted power steering and electric vehicle braking systems. Compounding these design challenges is the fact that the vehicle""s electrical system demands vary widely, irrespective of the engine operating speed which drives the alternator and changes through various driving conditions.
In addition to the challenges of providing high electrical output for the vehicle electrical alternator, further constraints include the desire to minimize the size of the alternator with respect to under hood packaging limitations, and its mass which relates to the vehicle""s fuel mileage.
In addition to the need of providing higher electrical output, designers of these devices further strive to provide high efficiency in the conversion of mechanical power delivered by the engine driven belt to electrical power output. Such efficiency translates directly into higher overall thermal efficiency of the motor vehicle and thus into fuel economy gains. And finally, as is the case with all components for mass-produced motor vehicles, cost remains a factor in the competitive offerings of such components to original equipment manufacturers.
One concern with higher power producing alternators is heat production. Fans mounted on the front of the alternator will circulate air across the front side to help cool the alternator, however, with higher output alternators, there is too much heat produced to be dissipated by these fans. Liquid cooled alternators dissipate the heat more effectively, but require extra size to accommodate cooling flow channels.
Therefore, there is a need for an improved alternator having flow channels to allow the alternator to be liquid cooled while still maintaining a small compact size.
In a first aspect of the present invention, an alternator includes an inner housing and an outer housing mounted over the inner housing with a pair of O-rings positioned therebetween to define a sealed flow chamber having a first flow channel, a second flow channel and an axial passageway interconnecting the first and second flow channels.
The first flow channel is defined by opposing first and second disk shaped portions of the inner housing, such that the first flow channel is a disk shaped cavity extending diametrically across the alternator. The second flow channel is defined by an inner diameter of the outer housing and an outer diameter of the inner housing, such that the second flow channel forms an annular jacket extending entirely around the alternator. The axial passageway is defined by an arcuate notch formed within the first disk shaped portion of the inner housing such that coolant is directed axially from the first flow channel into the second flow channel through the axial passageway.
An inlet extends from the first flow channel and is adapted to allow coolant to enter the first flow channel. The inlet is positioned diametrically across from the axial passageway such that coolant entering the inlet must flow diametrically across the alternator to reach the axial passageway. An outlet extends from the second flow channel and is adapted to allow coolant to exit the flow chamber. The outlet is positioned diametrically across from the axial passageway such that coolant entering the second flow channel must travel annularly around the alternator to reach the outlet.
In another aspect of the present invention, the inlet and the outlet are adapted to connect to a coolant system of an automobile such that engine coolant is circulated through the electric machine.
In still another aspect of the present invention, the alternator comprises a shaft rotatably supported within the inner housing by a pair of bearing elements, having a pulley mounted to a first end and a pair of slip rings mounted to a second end. A rotor assembly, including first and second pole pieces, is mounted onto the shaft with an excitation winding mounted between the first and second pole pieces and a stator assembly is fixedly mounted within the inner housing in functional engagement with the rotor assembly.